How to model ghamberson
I'm not sure it's the best method because it has some flaws but anyway:


Model all the big stripes on your mesh in Edit mode.
Give your object a Multires modifier, subdivide 5 times.
Switch to Sculpt mode and sculpt all the folds (Crease brush seems to work fine for this job).
Don't apply the Multires modifier, bake the normals using the method explained here by Pixxo, so that you can keep a rather low-poly object.